Chemical vapor deposition (CVD) reactors are used to produce polycrystalline silicon (polysilicon), the key raw material used in the manufacture of most semiconductor devices and silicon-based solar wafers and cells. The most widely used method for producing polysilicon is the Siemens reactor process generally according to the primary reactions below:HSiCl3+H2→3HCl+SiHCl+HSiCl3→SiCl4+H2 Net: 4HSiCl3→Si+2H2+3SiCl4 
In a related process, TCS is disproportionated to form silane (SiH4) and STC. The silane produced is used in many processes associated with semiconductors and other products, including making polysilicon in either a Siemens reactor or fluidized bed CVD process. The fluidized bed process makes silicon in irregular, but nominally spherical beads in diameters typically ranging up to about 2 mm diameter. Bead shaped polysilicon is equivalently referred to as granular polysilicon. The general chemistry of these reactions is as follows:4HSiCl3→SiH4+3SiCl4 SiH4→Si+2H2 
There is substantial patent literature regarding the CVD FBR process to make polysilicon. Lord et al., U.S. Pat. No. 5,810,934, SILICON DEPOSITION REACTOR APPARATUS provides a succinct background and numerous secondary references. Publications U.S. 2006/0105105 A1, U.S. 2009/0324479 A1, U.S. 2010/0068116 A1, and U.S. Pat. Nos. 8,535,614 B2 and 8,075,692 B2 describe related technology, the contents of which are hereby incorporated by reference. The problems routinely encountered are: 1) Formation of dust due to homogeneous nucleation of the silicon bearing gas and subsequent loss of valuable raw material; 2) Silicon deposition on the wall and internals of the FBR reducing the volume otherwise available for reactants and ultimately forcing shutdowns and cleanouts and/or rebuilds. If the FBR is made of brittle materials such as graphite or quartz, the differential coefficient of thermal expansion (CTE) between silicon deposited on the wall and the wall itself is likely to lead to reactor damage; 3) Inability to create the scenario where the reactive gas is sufficiently cold to avoid homogeneous nucleation (dust formation) and silicon beads hot enough to make shiny polycrystalline beads as opposed to amorphous silicon and/or a dusty surface that forms at lower bead temperatures; 4) Hydrogen or other gas inclusions exist within the silicon bead after deposition. A dense bead free of H2 or other gases is desired to avoid problems in downstream processing; 5) Finding suitable materials of construction for the FBR that are strong enough to resist breakage and which do not also contaminate the product is a continual challenge. For instance, metallic FBR's are durable and not susceptible to damage from differential CTE's but to date, no one has been able to avoid significant contamination of the product with a metal walled FBR; 6) Difficulties maximizing bead size; 7) Keeping bead size within an acceptably small range or particle size distribution; 8) preventing deposition within the feed nozzles where a silicon containing gas is fed.